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LCA of Nanocellulose

Nanocellulose is a promising, renewable nanomaterial. ScienceDaily has called the “wonder material” of the future. How cool is nanocellulose? Well, even Gizmodo and The Verge have talked about it. (Here is a very nice review by by Klemm et al. (2006) about the properties and applications of nanocellulose.)

In a recent publication (Nanocellulose Life Cycle Assessment), members of VTSuN reported the life cycle assessment of lab scale synthesis of nanocellulose. Four different synthesis methods were analyzed the trade offs in each case have been identified. You can read the abstract below and access the full article here.

Abstract:

“Nanocellulose is a nascent and promising material with many exceptional properties and a broad spectrum of potential applications. Because of the unique and functional materials that can be created using nanocellulose, pilot-scale development for commercialization has begun. Thus a thorough understanding of its environmental impact, covering the whole life cycle of nanocellulose, becomes the foundation for its long-term sustainable success. In this current study, four comparable lab scale nanocellulose fabrication routes were evaluated through a cradle-to-gate life cycle assessment (LCA) adopting the Eco-Indicator 99 method. The results indicated that for the chemical-mechanical fabrication routes, the majority of the environmental impact of nanocellulose fabrication is dependent upon both the chemical modification and mechanical treatment route chosen. For sonication, the mechanical treatment overshadows that from the chemical modifications. Adapting the best practice based on unit mass production was 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation followed by homogenization, as TEMPO oxidation resulted in a lower impact than carboxymethylation. Even though the fabrication process of nanocellulose presents a large environmental footprint markup relative to its raw material extraction process (kraft pulping), it still exhibits prominent environmental advantages over other nanomaterials like carbon nanotubes.”

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3 thoughts on “LCA of Nanocellulose”

Hello there! I love the idea of life-cycle analysis of nanomaterials, but my knowledge on life cycle analysis is somewhat limited. Can you give us, readers, a few examples of the trade offs that you saw between the different methods to produce nanocellulose? Could any of those synthesis techniques be considered “green”?

I guess this brings me to a bigger question: can LCA (life cycle analysis) be used to determine whether or not you can call a certain material a “green chemical”?

Dear Nina, thank you for raising a series of insightful questions, I will try to share some of my perspectives.

1. On trade-offs between different nano cellulose processing methods. Within the scope of this study, the trade-offs could be any of the following factors: harmful chemical wastes generated, energy consumption, production efficiency (this category also may include: ease of production, batch volume, size distribution, etc.). Take the comparison between sonication and homogenization for example, the sonication approach handles less volume per batch and is more handy in lab setting whilest its trade-offs are greater energy consumption on unit weight basis, broader size distribution (depending on the specific applications where broader distribution is preferred, this might as well be an advantage) and greater uncertainty of the environmental burden it carries.

2. Could any of these methods be considered as “green”? The short answer is “not clear”, if purely based on this current LCA study, since it only dealt with quantifying the total environmental impact and it did not set the baseline of “green”.

3. Can LCA be used to determine which chemicals are green? Probably not. This is because LCA is the method for quantifying the total environmental impact with an index while it does not deal with the standard (or the absolute baseline) for “green chemicals”. That being said, if we can figure out such a standard, assuming that is ever gonna happen, we can then determine whether a chemical is green or not by comparing its LCA index with that standard.

Qingqing, thanks for your reply. I would like to weigh in on points #2 and #3:

“2. Could any of these methods be considered as “green”? The short answer is “not clear”, if purely based on this current LCA study, since it only dealt with quantifying the total environmental impact and it did not set the baseline of “green”.”

My thoughts: There is no ‘baseline’ for green. The use of ‘green’ and ‘sustainable’ is always relative, never absolute, and it must always be understood as ‘process/product/chemical x is GREENER than y. (This ties in with the next point.)

“3. Can LCA be used to determine which chemicals are green? Probably not. This is because LCA is the method for quantifying the total environmental impact with an index while it does not deal with the standard (or the absolute baseline) for “green chemicals”. That being said, if we can figure out such a standard, assuming that is ever gonna happen, we can then determine whether a chemical is green or not by comparing its LCA index with that standard.”

My thoughts: Indeed LCA can be used to estimate what the environmental ‘hot spots’ are for one chemical/product/process relative to another, provided – and here’s the kicker – we are clear on what we those hot spots are and how we value them. Do we value water pollution over global warming potential? How would we weight these if we had to? (The answer is subjective may even depend on our geographical location – Someone in Canada might value these things differently than someone in sub-Saharan Africa. Also, these two ‘metrics’ global warming potential’ and ‘water pollution’ may by correlated or even have a self-propelling cause-effect cyclic relation, which further complicates the decision making.) Also, these environmental impact categories (Ozone Depletion Potential, Global Warming Potential, Carcinogenicity etc.) are sometimes bundled together as a single score. So when presented with an LCA result, we should dig deeper to see how our product/process/chemical fares in these individual categories.

Lastly, here’s my take on LCA as an instrument to measure sustainability:
LCA is not a decision-making tool, an algorithm or a crystal ball that will tell us A is greener than B. I think LCA can tell us, “Here’s the report card on chemical A and how it fares in Global Warming Potential, Land Use, Acidification Potential, Ozone Depletion Potential etc., and here’s the report card for chemical B.” It is then up to us to decide which of the two we should use. (Just my $0.02)